Schematic depiction of mitochondrial fission-fusion cycle, reticular-mitochondrial calcium signaling, and mitophagy. The processes mediated by Drp1, Mfn1 and 2, and Opa1 are indicated by arrows; ablation/inhibition of these factors results in accumulation of mitochondria like those before the arrow. Mfn1 and Mfn2 are both located at mitochondria and are largely redundant for OMM fusion (top), but only Mfn2 localizes to endo/sarcoplasmic reticulum (bottom left). Mfn2 also uniquely acts as a mitochondrial receptor for Parkin, facilitating its ubiquitination of OMM proteins and recruitment of autophagosomes (bottom right).